Recently, cases that an image by a computer and a dynamic image are displayed using a projection type image display device such as a liquid crystal projector and effective presentation is made using a pointing device increase, and a device that utilizes a gyrosensor for the pointing device is proposed. The pointing device utilizing the gyrosensor moves the body to a specific direction, samples the information of relative positions before and after the movement every fixed time, and transmits the relative positional information to the display device. The display device moves a selected position of a menu item included in a main menu on the screen based upon the received relative positional information, moves and the cursor and a point, pans and moves a picture in a picture.